Kersten W, Molenaar G J, Emmen J M, van der Schoot P
Department of Functional Morphology, Faculty of Veterinary Sciences, University of Utrecht, The Netherlands.
J Anat. 1996 Aug;189 ( Pt 1)(Pt 1):171-6.
The genital system of a dog with bilateral intra-abdominal testes is described. External virilisation was normal except for an empty scrotum. Internally there was a prostate of normal macroscopic and histological appearances and, bilaterally, a fully developed male genital tract. Testicular vasculature was normal. Cranial to each testis, there was a strong ligament lying at the free edge of the gonadal/genital mesentery and running between the cranial tip of the testis/epididymis and the area craniolateral of the ipsilateral kidney. It was impossible to push the testes into the inguinal canal because of this strong ligament. Caudal to each testis, there was an elongated whitish structure between the caudal pole of the epididymis and the area of the internal inguinal ring. On closer inspection this structure appeared to be the inverted and elongated processus vaginalis sac. There was a minor ligament at the free border of the inguinal fold of the genital mesentery between the tip of this inverted processus vaginalis and the adjacent junction of the cauda epididymidis and vas deferens. The findings suggest that persistence of the fetal cranial gonadal suspensory ligaments could have been the major aetiological factor in this case of cryptorchidism. Their persistence could have prevented caudal outgrowth of the processus vaginalis with its consequent development into an intra-abdominal papilla-like structure. Inappropriate persistence of the cranial suspensory ligaments in male rodents, pig, and cattle has been associated with insufficient exposure of their primordia to androgen during fetal life. It is uncertain whether a similar deficiency could underlie persistence of these structures in the present specimen. The findings add further weight to the hypothesis that regression of the cranial gonadal suspensory ligament in males is a key event in the process of testis descent. The human homologue of this ligament deserves more attention in the analysis and treatment of human cryptorchidism.
描述了一只双侧腹腔内睾丸犬的生殖系统。除阴囊空虚外，外生殖器男性化正常。内部有一个宏观和组织学外观正常的前列腺，以及双侧完全发育的雄性生殖道。睾丸血管系统正常。在每个睾丸的头侧，有一条强壮的韧带位于性腺/生殖系膜的游离边缘，在睾丸/附睾的头端与同侧肾脏的颅外侧区域之间延伸。由于这条强壮的韧带，无法将睾丸推入腹股沟管。在每个睾丸的尾侧，附睾尾极与腹股沟内环区域之间有一个细长的白色结构。仔细观察，这个结构似乎是倒置并拉长的鞘突囊。在这个倒置鞘突的尖端与附睾尾和输精管的相邻交界处之间的生殖系膜腹股沟褶游离缘有一条小韧带。这些发现表明，胎儿期头侧性腺悬韧带的持续存在可能是该隐睾病例的主要病因。它们的持续存在可能阻止了鞘突的尾侧生长，从而使其无法发育成腹腔内乳头状结构。雄性啮齿动物、猪和牛的头侧悬韧带持续存在不当与它们的原基在胎儿期雄激素暴露不足有关。目前尚不确定类似的缺陷是否是本标本中这些结构持续存在的基础。这些发现进一步支持了以下假设：男性头侧性腺悬韧带的退化是睾丸下降过程中的关键事件。在人类隐睾症的分析和治疗中，这条韧带的人类同源物值得更多关注。
